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Collective defence

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Collective defence is the key function of the alliance.

Since the end of the Second World War, NATO has been one of the key guarantors of our security on the European continent. The Strategic Concept underscores that the core function of the Alliance is the mutual defence obligation contained in Article 5 of the Washington Treaty. The Concept also states that NATO may take action to deter and defend against any threat of aggression. NATO possesses both nuclear and conventional capabilities, as well as missile defence capabilities. With these assets, it can meet the security policy challenges of the 21st century and ensure the protection of its member countries.

At the NATO Summit in Lisbon in November 2010, the Alliance’s Heads of State and Government made the fundamental decision to develop a NATO ballistic missile defence (BMD) capability within the framework of the Alliance’s collective defence, in order to ensure that the populations and territory of NATO Allies are protected as well as possible. At the NATO Summit in Chicago in May 2012, attainment of an interim BMD capability was declared. NATO will gradually further develop its own air defence system so that, by the year 2020, it will have a fully-operational missile defence capability.

Mutual defence can take different forms: In the history of the Alliance, Article 5 was invoked only once, after the terrorist attacks of 11 September 2001 in the United States. In practical terms, mutual defence means that Allies support each other and defend one another against armed attacks.

Assurance measures on the territory of eastern NATO Allies are an example of such support. They were agreed at the 2014 NATO Summit in Wales, in response to the annexation of Crimea in March 2014 in violation of international law, as well as Russia’s continued destabilisation of eastern Ukraine, and they include NATO air policing and exercises. Support can also be provided in response to security challenges in the southern arc of crisis, e.g., through enhanced aerial surveillance over Turkey. These measures are defensive in nature, proportionate, and do not violate any of NATO’s international obligations or the NATO-Russia Founding Act. In view of the persisting threats and challenges, NATO Allies at their summit meeting in Warsaw in July 2016 also agreed to establish an enhanced forward presence on a rotational basis, consisting of multinational brigades in the three Baltic states and in Poland. In 2017, Germany will assume the lead role for the brigade in Lithuania.